The present invention relates to a bipolar high frequency treatment tool having a pair of electrodes at the distal end of an inserting portion to be inserted into a body cavity through an endoscope.
A monopolar high frequency treatment tool is commonly used for endoscopic surgery. The monopolar high frequency treatment tool utilizes an electrode in combination with a counter plate attached to the body surface of a patient so that high frequency current flows between the electrode and the counter plate.
In the surgery utilizing the monopolar high frequency treatment tool, electric leak may occur if the patient comes in contact with a conductor other than the counter plate, which causes decrease of current effective to the operation and/or the surgeon to get burned.
Japanese patent provisional publication No. P2000-271128 discloses a bipolar high frequency treatment tool that overcomes the disadvantages of the monopolar high frequency treatment tool. The treatment tool disclosed in the above mentioned publication has a pair of electrodes mounted at the distal end of the treatment tool. The electrodes are arranged so as to open and close like pincers by a remote manipulation from the proximal end of the treatment tool. The electrodes are connected to the positive and negative terminals of a high frequency power supply, respectively, so that high frequency current flows through the tissue of the patient pinched between the electrodes.
The electrodes of the bipolar high frequency treatment tool have to be insulated from each other so that the high frequency current does not flow between the electrodes except the portions thereof that are expected to pinch the tissue of the patient. In order to achieve this, the electrodes disclosed in the above-mentioned publication are made of electrical insulating material such as plastic and ceramic with metal layers partially evaporated thereonto.
The electrodes, however, made of nonmetallic material are relatively low in strength and are easy to be broken. Further, the evaporated metal layer may come off from the electrode when, for example, it is rubbed against the inner wall of the channel of the endoscope through which the high bipolar frequency treatment tool is inserted into the body cavity.
For the forgoing reasons, there is a need for a bipolar high frequency treatment tool that has high strength while providing good insulation between the pair of electrodes.